Re: [f2fs-dev] [PATCH v2] f2fs: add iostat latency tracking for direct IO

[Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

On 5/8/26 21:59, liujinbao1 wrote:
> From: liujinbao1 <liujinbao1@xiaomi.com>
> 
> F2FS did not collect iostat latency for direct IO reads and writes,
> hook iomap_dio_ops.submit_io to bind an iostat context and record the
> submission timestamp. Replace bi_end_io with f2fs_dio_end_bio() to
> collect IO latency on completion before calling back to the original
> iomap_dio_bio_end_io(), to add iostat latency tracking support for
> F2FS DIO.
> 
> Signed-off-by: shengyong1 <shengyong1@xiaomi.com>
> Signed-off-by: liujinbao1 <liujinbao1@xiaomi.com>
> ---
> v2:
> - add f2fs_dio_iostat_start() to avoid duplicated code
> and CONFIG_F2FS_IOSTAT guard
> ---
>   fs/f2fs/file.c   | 35 +++++++++++++++++++++++++++++++++++
>   fs/f2fs/iostat.c |  2 +-
>   2 files changed, 36 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 091a9db29228..d35e3cf158bf 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -4790,6 +4790,30 @@ static bool f2fs_should_use_dio(struct inode *inode, struct kiocb *iocb,
>   	return true;
>   }
>   
> +#ifdef CONFIG_F2FS_IOSTAT
> +static void f2fs_dio_end_bio(struct bio *bio)
> +{
> +	struct bio_iostat_ctx *iostat_ctx = bio->bi_private;
> +	void *orig_bi_private = iostat_ctx->post_read_ctx;
> +
> +	iostat_update_and_unbind_ctx(bio);
> +	bio->bi_private = orig_bi_private;
> +	iomap_dio_bio_end_io(bio);
> +}
> +
> +static void f2fs_dio_iostat_start(struct f2fs_sb_info *sbi, struct bio *bio)
> +{
> +	void *bi_private = bio->bi_private;
> +
> +	iostat_alloc_and_bind_ctx(sbi, bio, bi_private);
> +	iostat_update_submit_ctx(bio, DATA);
> +	bio->bi_end_io = f2fs_dio_end_bio;
> +}
> +#else
> +static inline void f2fs_dio_iostat_start(struct f2fs_sb_info *sbi,
> +					 struct bio *bio) {}
> +#endif
> +
>   static int f2fs_dio_read_end_io(struct kiocb *iocb, ssize_t size, int error,
>   				unsigned int flags)
>   {
> @@ -4802,8 +4826,18 @@ static int f2fs_dio_read_end_io(struct kiocb *iocb, ssize_t size, int error,
>   	return 0;
>   }
>   
> +static void f2fs_dio_read_submit_io(const struct iomap_iter *iter,
> +					struct bio *bio, loff_t file_offset)
> +{
> +	struct f2fs_sb_info *sbi = F2FS_I_SB(iter->inode);
> +
> +	f2fs_dio_iostat_start(sbi, bio);
> +	blk_crypto_submit_bio(bio);
> +}
> +
>   static const struct iomap_dio_ops f2fs_iomap_dio_read_ops = {
>   	.end_io = f2fs_dio_read_end_io,
> +	.submit_io = f2fs_dio_read_submit_io,
>   };
>   
>   static ssize_t f2fs_dio_read_iter(struct kiocb *iocb, struct iov_iter *to)
> @@ -5082,6 +5116,7 @@ static void f2fs_dio_write_submit_io(const struct iomap_iter *iter,
>   	enum temp_type temp = f2fs_get_segment_temp(sbi, type);
>   
>   	bio->bi_write_hint = f2fs_io_type_to_rw_hint(sbi, DATA, temp);
> +	f2fs_dio_iostat_start(sbi, bio);
>   	blk_crypto_submit_bio(bio);
>   }
>   
> diff --git a/fs/f2fs/iostat.c b/fs/f2fs/iostat.c
> index ae265e3e9b2c..232fdec036c1 100644
> --- a/fs/f2fs/iostat.c
> +++ b/fs/f2fs/iostat.c
> @@ -254,7 +254,7 @@ static inline void __update_iostat_latency(struct bio_iostat_ctx *iostat_ctx,
>   	struct iostat_lat_info *io_lat = sbi->iostat_io_lat;
>   	unsigned long flags;
>   
> -	if (!sbi->iostat_enable)
> +	if (!sbi->iostat_enable || iostat_ctx->submit_ts == 0)

Which path we will see zeroed .submit_ts?

Thanks,

>   		return;
>   
>   	ts_diff = jiffies - iostat_ctx->submit_ts;



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